A liquid crystal display device including a transmissive liquid crystal display panel and a backlight unit is used as a flat-screen display device. The backlight unit is disposed behind the liquid crystal display panel. The backlight unit includes fluorescent lamps such as cold cathode fluorescent lamps (CCFLs) that define light sources, and is arranged to illuminate the liquid crystal display panel from behind with light emitted from the fluorescent lamps while controlling the properties of the emitted light. The light with which the liquid crystal display panel is illuminated passes through the display panel, making an image displayed visible on a front side of the liquid crystal display panel.
FIGS. 10A and 10B are views showing a schematic configuration of a conventional liquid crystal display device that is generally used. As shown in FIGS. 10A and 10B, a liquid crystal display device 50 includes a bezel 51, a liquid crystal display panel 52, and a backlight unit 53. The bezel 51 functions as a frame of the liquid crystal display panel 52, and is arranged to hold a border portion of the liquid crystal display panel 52. The liquid crystal display panel 52 includes two glass plates that are stuck to each other by filling liquid crystals between the glass plates.
The backlight unit 53 includes a frame 54, optical sheets 55 to 57, a diffusion plate 58, fluorescent lamps 59, a reflection sheet 60 and a backlight chassis 61. The frame 54 has the shape of a frame, and is arranged to fix the optical sheets 55 to 57 and the diffusion plate 58 to the backlight chassis 61, keeping them stacked.
The optical sheets 55 to 57 and the diffusion plate 58 are arranged to control the properties of light that is emitted from the fluorescent lamps 59 and enters the liquid crystal display panel 52. The optical sheets 55 to 57 are defined by a stack of three sheets of a diffusion sheet, a lens sheet and a reflective polarizing sheet, each of which has a thickness of 0.1 to 0.3 mm. The diffusion plate 58 is made of resin to have a thickness of about 2 mm, and is disposed under the optical sheets 55 to 57.
Disposing the diffusion plate 58 above the fluorescent lamps 59 enables uniform luminosity of the light within a light emitting surface of the diffusion plate 58 while preventing the fluorescent lamps 59 from casting their shadows (lamp images) on the light emitting surface. The reflection sheet 60 laid under the fluorescent lamps 59 is arranged to reflect the light emitted from the fluorescent lamps 59 toward the liquid crystal display panel 52.
The chassis 61 has the shape of a box of low height, and is capable of housing the plurality of fluorescent lamps 59. The light emitted from the plurality of fluorescent lamps 59 arranged in parallel inside the chassis 61 is, together with the light reflected from the reflection sheet 60, transmitted through the diffusion plate 58, the optical sheets 55 to 57 and the liquid crystal display panel 52, and is visually observed on the observer's side.
In this configuration, diffusion plate holding members 62, as disclosed in PTL1, are provided to stand on a lamp housing surface 61a of the backlight chassis 61. The diffusion plate holding members 62 are arranged to hold the diffusion plate 58 from below, which prevents the diffusion plate 58 from being warped by its own weight. Because shadows of the diffusion plate holding members 62 are casted to some degree on the light emitting surface of the diffusion plate 58, if the diffusion plate holding members 62 are disposed so as to hold the diffusion plate 58 at a center portion thereof, the shadows of the diffusion plate holding members 62 appear obtrusively in a center portion of the liquid crystal display panel 52. In order to make the shadows unobtrusive, the diffusion plate holding members 62 are disposed on either side of the center portion of the diffusion plate 58 so as to surround (sandwich) it as shown in FIGS. 10A and 10B.